This invention relates to a process for the production of compounds containing hydroxyl groups from polyurethane-polyurea and/or polyurea waste materials which are suitable for use in the polyisocyanate addition polymerization process. In this process, the waste material is decomposed with alcohol and the alcoholysis product is further reacted to reduce the content of low molecular weight, sterically unhindered aromatic amines.
The decomposition of plastics obtained by the polyisocyanate addition polymerization process with alcohols is known in principle. However, when polyurethaneopolyurea and/or polyurea waste materials are decomposed by alcoholysis, it is difficult to recover usable products. Working up plastics which have been produced using poly-isocyanate mixtures of the diphenylmethane series and aromatic diamines as chain extenders (i.e., PUR waste materials with a high content of urea groups) is particularly difficult.
Alcoholysis products of polyurethane-polyurea and/or polyurea waste materials with a high content of urea groups are characterized by a relatively high content of low molecular weight, primary aromatic amines, particularly sterically unhindered primary aromatic amines (B. Naber: "Recycling of Polyurethanes (PUR)", Kunststoff-recycling-Tagung der TU Berlin [Plastics Recycling Report of the Technical University of Berlin], 01.10.91).
These characteristics of the alcoholysis product may limit considerably its usefulness in isocyanate addition polymerization processes. For example, a high content of low molecular weight primary aromatic amines has a negative effect on the processability of alcoholysis products of this type (e.g., in reaction injection molding processes (RIM)), due to the high reactivity of such amines. This high reactivity causes short flow distances and results in inability to fill complicated molds. A high content of low molecular weight primary aromatic amines (particularly sterically unhindered primary aromatic amines) can cause inferior properties such as high glass transition temperature, low ultimate tensile strength and low elongation at tear in polymers produced with that alcoholysis product.